Fluid actuated control system



July 3. 1945. p. MACkENZIE 2,

FLUID ACTUATED CONTROL SYSTEM Filed June. 18, 1941 5 she ts-s at 1- J ZlE FLUID ACTUATED CONTROL SYSTEM D. hlACKEN .July 3; 1945.

Fild June 18. 1941 5 Sheet s-She et 3 uvvevvro CA E/Vz/A',

Don 440% ar' y 1945- D. MACKENZlE Y 2,379,536

I FLUID ACTUATED CONTROL SYSTEM I Filed June 18, 1941 s Sheets-Sheet 4 4 ice/Er;

.ST'W 3 /52 y 1945' D. MACKENZIE L 2,379,536

- FLUID ACTUATED"CONTRQL SYSTEM Filed June 18, 1941 5 sheets-sh et 5 Potented July 3, 1945 Faun) ACTUATED common sYs'rEM Donald MacKenzie, Cheltenham, assignor to Dowty Equipment Limited, 'Cheltenham,

England Application June 18, 1941, Serial ivofsaam in Great Britain Jules, 1940 6 Claims.

The present invention relates to fluid actuated control systems and is particularly concerned with the provision of a satisfactory system in which various operations have to be performed in a certain order, which may not necessarily be the same order as between operation in one sense compared with that in another.

A typical example of such a system is one winch involves extension and retraction of aircraft alighting gear, which, in the retracted condition, is housed in a compartment closed by fairing doors, the alighting gear and the doors being-operable by jack means. Thus, when it is required to edect extension of a retracted untier-carriage, it is necessary first to open the .iairing doors and then to extend the undercarriage, the fairing doors remaining open so long as the undercarriage remains extended. Conversely, at the termination of retraction operation, the

utilisation of the circuit involving indicator means for controlling the operative relationship iairing doors must close, and it is of theutmost importance that they should not start to close beiore the undercarriage is retracted far enough to avoid any possibility of it fouling the'fairing doors, as it might well do if the doors started to close too soon. That typical system will later he described more particularly in the ensuing description, but it is to be understood that it may be varied considerably for different op-- erations where jack or equivalent devices have to beactuated in some pro-determined relationship; for instance, cases may arise where it is desirable that wing flaps should not be operable until the undercarriage is extended, or conversely should not be operable in the opposite sense until the undercarriage is fully retracted. Again, the operations involved may include the control of a variable pitch airscrew.

The present invention consists in a fluid actuated control systemlincluding at least two jacks or like receiver means operable in a predeterruined relationship in at least one sense of operation, a control device manually operable for controlling movement of at least one of said receiver means, and a control automatically oper--- able on completion of an electric circuit by switch meansactua'ted at some predetermined stage of the rnoveinent induced by actuation of the manuai devicejgvhereby to control the operative relationship c? said jack means.

On air craft there is frequently provided an electrically operated indicator device controlled hyelectrical contacts serving to complete an indicating circuit, for instance, when a retractable undercarriage is fully extended and also when it is iully'retracted, and the invention includes the jacks;

of the jack means. i a

It will be realised that any particular jack or equivalent receiver means concerned with one operation or a set of operations may be at least duplicated and that likewise the various courations which are to be inter-related are not conlined merelyto two, but may be three or'even more. l

In order that it may be clearly understood and readily carried into eflect, the invention is hereinafter described with reference to the accompanying digrammatic drawings, of which:

Figure 1 is a piping and wiring circuit diagram relating to a typical lay-out for operation of two undercarriage jacks and two fairing door jacks;

Figure 2 is a. sectional elevation showing the electrically operated automatic valve which controls the relationship required between the Figure 3 is a piping and wiring circuit diagram illustrating a typical lay-out for operation of bomb-hatch doors and latches;

'Figure 4 is an end elevation partly in section of an electrically operating automatic valve which controls the relationship between the door and latch actuating jacks; and" Figure 5 is a section on the line VV of Figure 4.

The arrangement shown in Figure 1 is in ac cordance with the typical example hereinbeiore referred to, in which when the undercarriage is to be extended from a retracted condition the fairing doors have to open whereafter the undercarriage is extended, the fairing doors remaining open, while in retraction it is essential that the undercarriage should first retract before the fairing doors close.

Referring now to Figure 1, fluid pressure from any conveniently available source, preferably an engine driven hydraulic pump, is fed from the pipe line 8 to-the rotary flow reversing valve I which is provided with a handle 3 for setting the valve to perform the requisite operations. The

pipe line a conveys fluid preferably through a variable flow restriction valve ill with branches 9', t" to the jack unions H, which in this case afiord fluid flow passage for retraction of the undercarriagejacks l2,;and during retraction of the jacks return fluid flows through the branches l3, l3" along the pipe line l3,to the control valve and then along the pipe I4 to the fluid pressure source. The pressure conduit l5 conthe port nects the pipe line 9 with the electrically operated control valve l6 which is arranged to permit fluid flow to the fairing jacks l1. Actuating fluid passes through the pipe line l8, with branches l8, l8", for fairingjack extension and automatic function of the valve [6. The function of the relay 2| is to prevent either fairing door Jack being energised before both undercarriage jacks are fully retracted. (Alternatively, two switches may be incorporated, wired in series, in order to achieve the same eflect.) The reference numeral 22 indicates plunger operated switches which, on being engaged by the switch actuating arms 23 complete the circuit to the indicator 24 for conveying to the pilot a signal that the undercarriage is properly up. Bridging of the switch contacts not only places the indicator device in circuit with an available current source, but also brings the relay 2! into the current supply circuit. 7

The system is of the kind in which actuating pressure is "live, being fed to the extension and retraction lines according to the setting of the reversingvalve 1. When flow is to the Jacks through the conduits 9', 9 and I9, I9" return flow is through the conduits l3, l3 and I8, I8" back through the valves l6 and I along the conduit H to the supply reservoir (not shown).

The invention will now best be understood with reference to the operation of the system, the explanation of which involves detailed descriptilon of the electrically controlled automatic valve 6.

Let it be assumed that the undercarriage is own and the fairing doors are open, as they are required to be in the circumstances. If then the actuating lever 8 of the rotary manual controlled valve 1 is moved to the up position, fluid flow is directed from the pressure line through the valve 1 along the pipe line 9 and branches 9', 9" to retract the plunger-s of the jacks l2.

Pressure fluid also passes along the pipe line 45 to the valve l6. Entering the valve I 6 through la (see Fig. 2) pressure liquid is prevented by a non-return valve 25 from passing out of the valve through the port I90. and along the pipe line l9 and branches l9, l9" to the fairing jacks l1. Likewise, a spring-loaded ball valve 26 closes the port 21, and hydraulically locks the ball 28 to its seat. The fluid can not, therefore, pass through the valve casing l 6 under such conditions, but can only pass along the conduits 9', 9" to the undercarriage jacks 12, to retract the undercarriage.

Immediately the undercarriage reaches its fully retracted position, the indicator switches '22 are actuated and not only is the indication undercarriage up given at the indicator 24, but also the circuit to the relay 2! is completed,

' with the result that the, solenoid 20 is energised and the ball valve. 26 lifted to permit passage of oil past the spring-loaded ball valve 28, through the valve chamber 29, port 30, to the chamber 30 to lift the piston 3| against resilience and open the valve 25. Immediately the valve 25 is opened, pressure fluid can-find its way out through the port I So along the pipe line l9 and branches I9, l9" to the retraction union of the fairing Jacks l'l thereby to close the doors. It will beobserved that the valve body 48 includes a piston 3! which is paired with the piston 3| and is operated for opening therewith to control the valve 25' similar in nature and function to 25. When the valve 25' is open, pressure fluid returning from the fairing jacks I! can find its way from the pipe line l8 into the port Na and out through the port 32a to return through the pipe line 32 back into the circuit.

"The valve 25' has an additional function in that when it is actuating as a non-return valve, it serves to afford a hydraulic lock preventing circulation of pressure fluid such as would be necessary to permit retraction of the fairing door jacks, and as a consequence of that hydraulic lock the fairing doors are securely main tained open against loads induced by the slip stream pressure before the undercarriage is as pressure fluid passes through the pipe line 32 in the direction shown by the arrow in Fig. l

to circulate through 32a and Illa of the control valve It to extend the fairing jacks l5 through the pipe line l8 and branches l8, l8". Relief for fluid in the opposite ends of the fairing jacks is afforded through lines I9, l9 and 19" back through port 19a, past valve 25, and out through port I5a, conduit l5, and valve I toreturn conduit I4.

A non-return valve 33 is provided in the .body

. of the solenoid. to isolate the chamber,29 from the reservoir return, pipe 34 from the solenoid when the ball 26 is lifted. Pressureliquid passing. the non-return valve 28 cannot flow to the return pipe 34 through the solenoid when the ball valve 26 is lifted by reason of the fact that the additional non-return valve prevents entry into the return pipe 34 and pressure liquid from the undersides of the pistons 3|, 3| therefore passes on de-energisation 'cf the solenoid through the body of thesolenoid past the nonreturn valve 33 to the reservoir return pipe 34.

fI'he solenoid is continuously energized after retraction-in order to maintain pressure on the fairing jacks, but the solenoid circuit may be broken after retraction is completed and the fairing doors retained in position by thehydraulic lock -or mechanical latches. Additional means to obtain interruption of the solenoid circuit would be a switch or switches operated by the fairing doors in their fully closed ,position.

The solenoid consumes a small amount of current only, and can be kept continuously energised without undue temperature rise.

The arrangement hereinbefore described deals with a single sequence operation; that is to say,

'the system operates to prevent fairing door the undercarriage remains, extended) is required to ensure opening of the fairing doors prior to extension, extension of the undercarriage (fairing doors remaining open while and, reversing the procedure, first retraction of the undercarriage and then closure of the fairing doors at the end of the retraction operation, a modified arrangement is required. A typical double sequence operation is shown with reference to Figure 3, which-illustrates a system for controlling bomb hatch door latches for locking and unlocking and for appropriately actuating the bomb hatch doors for opening and closing. The sequence required in such a case is (assuming bomb hatch doors closed) (1) unfasten latches, (2) open bomb hatch doors, (3) close bomb hatch doors, and (4) refasten latches. Jack means are provided for latch operation and for opening and closing the bomb hatch doors. The double sequence operation described with reference to Figure 3 requires a modified construction of valve which is illustrated in Figures 4 and 5, to be read in conjunction with Figure 3.

Referring now to Figure 3, the jacks 35, which are selectively operable for retraction and extension to open and close the bomb hatch doors,

are supplied with pressure fluid for extension through the conduit. 36, and for retraction through the conduit 31. The latch actuating jacks are indicated at 38 and are supplied with pressure fluid for extension to release the latches through the conduit 39 and conversely with pressure fluid for retraction'through the conduit All. The plungers of the jacks 38 have switch actuating arms38' which in the fully retracted condition of the plungers of the jacks 38 make contact with the plungers ii of the switches Hi. The switches 66 closed but are opened by the arms 38'. The switches 62 are normally open and have plungers 32' which are engaged by, the arms 38' when the plungers reach their fully extended condition. The bomb hatch door actuating jacks 35 have switch actuating arms 35' which, in the retracted condition of the jacks, engage the plungers 53' of the switches 43 to close the switches which are normally open. The switches id are normally closed but are opened bythe actuating arms 35' in the extended condition of the jacksg35. Closure of the switches ti, t2, t3 and M, completes the circuit from the battery 35 to one or other of the solenoids t6, 41,'whereby to determine the operational sequence of the system under control of the valve, indicated generally at 8. The valve 63 is supplied with pres- I sure fluid through the connection 69 on operation of a manual control valve (not shown) similar to the selector'valve 1 shown in Fig. 1 when it is required to open the bomb doors, during which operation return flow of liquid is through the connection 59 back through the control valve and supply reservoir, not shown. Conversely, when the bomb doors require to be closed pressu e flows into the valve 58 through the connection 50 and out from the connection 619 back to the reservoir.

The nature of the valve 58 is best seen by reference to Figure 5. The conduit 36 is con nected from the extension side of the jacks 35 to the port 35. Similarly, the conduit 39 for extension of the latch jacks connects to theport 39. The conduits 31 and Ni lead into the valve. 48 through the connections 31' and 40'.

The. connections 49' and 50 are appropriately I the switch actuating arms 38 engage the'plung-' are normally 5 tween the connection and the closed end of the piston 56 slidable in the bore 51. The stem.

of the non-return valve 52 is carried by the guide 58 extending from the piston 58 sliding in the boreBU. Likewise, the stem of the non-return valve 54 is engaged by the guide 6| extending from the piston 62 sliding in the bore 63. The

bore 60 behind the piston 59 is in communication with the bore 51 on one side of the piston .58 through the passage 60:; and the bore 63 behind the piston 62 is in communication with the bore 51 on the other side of the piston 56 through the passage 63a.

The system described with reference to Figures 3, 4 and 5, will now best be understood by describing an operational sequence, it being assumed that the sequence starts with the bomb hatch doors closed and latched. Thus the manual control valve is'actuated to deliver pressure fluid to the valve body 48 through the connection 69. The pressure fluid opens the nonreturn valve 52 to the conduit 39 and extends the plungers of the jacks 38. Fluid pressure internally. of the bore 51 also moves the piston '56 to open the non-return valve 53 so that return fluid can flow along the conduit it through the connection til past the non-return valve 53 out through the connection 50 back to the reservoir. When the plungers of the jacks 38 are fully extended, the latches are unlocked and ers 42' to energise the solenoid 56.

It may here be mentioned that the solenoids t6 and t1 and their internal valve arrangement, are the same as that described with reference to Figure 2, but in the present case a port corresponding to the port 30, referred to in Figure 2, is opened by energisation of the solenoid 36 to deliver pressure fiuid supplied to the valve through the connection "35 to the closed, end of the bore 53 and actuate the piston 52 to open the non-return valve 56, and the solenoid $1 in the same way establishes communication bethe bore 60 to actuate the piston 55 for opening the non-return valve 52.

Thus, energisation of the solenoid t5 by closing of the switches t2 causes the non-return valve 541 to open, zthblS to release the fluid from the door jacks 35 through conduit 31? to conduit 5, leading to the reservoir, so that pressure fluid flowing through the connection it then may open the non-return valve 55!! allowing the passage of pressure fluid to the conduit 55 for extension of the bomb hatch door jacks 35. When the plungers of the jacks 35 are fully extended the bomb hatch doors are iully open and the switch actuating arms 35 open the switches M to de-energise the solenoid, whereupon the spring loading of the non-return valve 5% causes it to close, pushing the pressure fluid in the closed end of the bore 63 back to the reservoir through the body of the solenoid and conduit M.

To close the bomb hatch doors, the control lever of the manual control valve is reversed and pressure fluid enters the body of the valve 48 through the connection 50 from which return flow through .themanual control valve to reservoir can pass out of the body 48 through the connection 48.

Pressure fluid entering the connection 58 causes the non-return valve I4 to open, at the same time actuating the piston 56 to open the non-return valve Slto permit return flow'from the jacks 85 through the conduit 38 pastthe non-retum valve 5| and out to reservoir through the connection 49. When the Jacks 35 reach their fully retracted position the bomb hatch doors are closed and their switch actuating arms 35 close the switches to energise the solenoid 4?, Enerelection of the solenoid 41 directs pressure fluid to the closed end of the bore 60 with the result that the piston 59 is actuated to open the nonreturn valve 52.120 permit return flow from the conduit 39 and latch jacks 38 back to reservoir through the connection 49, whereupon the noneretum valve 53 is opened by the pressure fluid which is directed along the conduit db to retract the plungers oi'the jacks 3d and secure the latches on the already closed bomb hatch A doors. when the jacks 3d are fully retracted 1. Valve mechanism for controlling a fluid operated element, comprising a valve body having a pressure fluid supply and discharge connection, a connection to said fluid operated element, a valve in said valve body having its opposite sides exposed to the pressurein said respective connections and adapted to be pressedto its seat by a pressure in the supply and discharge connection superior to pressure in the fluid omrated element connection, apiston engageable with said valve to open it, a cylinder receiving said pisto a bypass duct between said fluid supply and d1 barge connection and said cylinder, andelectrically operated means controlling said by-pass duct and operable to open it for supply of fluid to said cylinder to move said piston .to open said valve against pressure in said supply and discharge connection superior to pressure in said fluid op erated element connection, and said valve and piston being mechanically unconnected for move ment of said valve to open position independently of movement of said piston by pressure in said fluid operated element connection superior to the pressure in said supply and discharge connection. I

2. Valve mechanism for controllinga fluid operated element, comprising a valve body having a pressure fluid supply and discharge connection, a connection to said fluid operated element, a valve in said valve body having its opposite sides exposed to the pressure in. said respective connections and adapted to be pressed to its seat by pressure in the supply and discharge connection superior to pressure in the fluid operated element a connection, fluid actuated valve operating means operable to open said valve, a by-pass duct between said fluid supply and discharge connection and said valve operating means, and electrically operating means to open said valve against presperior to pressure in said fluid operated element connection, and said valve and valve operating means being mechanically unconnected !or movement of said valve to open position independently or movement of said valve operating means by pressure in said fluid operated element connection superior to the pressure in said supply and discharge connection.

3. Valve mechanism for a double-acting fluid jack, comprising a valve body having therein a supply connection communicating with a source of fluid under pressure, a connection to the jack for flow of fluid thereto, a jack duct in said valve body between said connections, a second connection 'to the jack for flow of fluid therefrom, and a fluid discharge connection, a non-return valve between said second jack connection and said discharge connection, normally urged to its seat by pressure thereon of fluid entering said valve body from said second jack connection, a piston movable in a piston chamber formed in said valve iii? body, operable to engage aid non-return valve for raising it from its seat against the pressure of fluid in said second jack connection, said valve body having a passage independent of said Jack duct between the piston chamber and said fluid supply connection for actuation of said piston to open said non-return valve by pressure of fluid thereon,an'd solenoid operated valve means controlling communication between said supply connection and the piston chamber to eflect valve opening movement of the piston only when said solenoid is energized.

i. In an aircraft structure, a fluid system for actuating an initiall operable fluid operated element and a secondarily operable fluid operated element, comprising pressure fluid supply and discharge conduits, a valve body having a connection to each of said fluid supply and discharge conduits, a feed connection to each of said fluid operated elements, and a return connection from each of said fluid operated elements, said valve body being apertured to establish communication between the supply conduit connection and both fluid operated element feed connections, and between the discharge connection and both of said fluid operated element return connections, valve means in said valve body interposed between said discharge connection and the secondarily oper able fluid operated elementreturn connection, and operating means for said valve means energizable to open the same for flow of fluid through said secondarily operable fluid operated element return connection, and means associated with the initially operable fluid operated element operatively connected to said valve operating means to energize suchmcans for opening said valve at a predetermined stage of the movement of said initially operable fluid operated element, to enable fluid to return through said valve body to said discharge conduit from said secondarily operable fluid operated element,- and simultaneously operated means controlling said by-pass duct and. operable tq open it fo s pp y of fluid tosaid valve to enable fluid to be supplied from said valve body to such secondarily operable fluid operated element.

5. In an aircraft structure, .a fluid system for actuating two fluid operated elements, a pressure 'fluid supply and discharge conduit connected dition to the other fluid operated element, a valve "in said valve body interposed between said fluid supply and discharge connection and said fluid 'operat'ed 'element connection, said valve being ferential pressures on said valve to "permit unidirectional flew of fluid between said connections,

electrically controlled pressure fluid operating means for the valve energizable to open said "ply of fluid under pressure through said supply and discharge conduit to said fluid operated elements and .the relief of pressure in said supply and discharge conduit for discharge of fluid vtherethrough from said fluid operated elements.

6. In an aircraft structure, a fluid system for actuating two fluid operated elements, a pressure fluid supply and discharge conduit connected directly to one oi said fluid operated elements, a valve body having a connection to saidfluid supasvassc movable in one direction by the operation of difsaid fluid operated elements.

ply and discharge conduit, and a further connection .to the other fluid operated element, a valve in said valve body interposed between said fluid supply and discharge connection and said fluid operated element connection, said valve being movable in one direction by the operation of diflerentiai pressures on said valve to permit unidirectional flow oi fluid between said connections, operating means for the valve energizableto open said valve positively for flow of fluid in the opposite direction between said connections, but unconnected to said valve for movement of said valve independently of said valve operating means under such diflerentialpressure conditionameans operable by said first fluid operated element at a predetermined stage in its movement to control energization of said valve operating means for effecting positive movement oi'said valve, and means to control selectively the supply of fluid under pressure through said supply and discharge conduit to said fluid operated, elements and the relief of'pressure in said supply and discharge conduit for discharge of fluid therethrough from DONALD MACKENZIE 

